Music, artful arrangement of sounds across time. This definition is obviously very broad, but a narrower one would exclude too much. Music is part of virtually every culture on Earth, but it varies widely among cultures in style and structure. Definitions of music can change dramatically over a short time, as they have across the world during the 20th century.

Can music exist without sound? Some philosophers argue that music should be defined as a kind of “mental image” and that the physical aspects of sound are simply by-products of this image. If you think you can have a musical experience by imagining the sound of a piece of music, then you think music can exist without sound. But most musical experiences involve producing or listening to physical characteristics of sound such as pitch and timbre (quality comparable to texture or color in sight).

Is the tape-recorded sound of a large metal-stamping machine music? Are 4 minutes and 33 seconds of silence music? Is the activity of reading a list of hundreds of seemingly unrelated objects, activities, and states of mind music? Each of these “works”, as well as many other sounds (or nonsounds), has been copyrighted as a musical composition, performed, and recorded in the 20th century. One of the legacies of 20th-century music is to have blurred the definition of music as never before.

Other experts argue that whether any particular pattern of sounds (or our mental image of this pattern) is or is not music hinges on the musical culture into which we were born and in which we have grown up. In other words, whether sounds are music or not has more to do with learning than with anything about the physical characteristics of the sounds or the inborn characteristics of people. An American or European, hearing for the first time a Javanese gamelan performance or singing by the Ewe people of West Africa, might feel disoriented and disappointed by the unfamiliar and seemingly meaningless sounds of these kinds of music. Similarly, Javanese or Ghanaian listeners might feel every bit as disappointed when they first hear the music of Austrian composer Franz Schubert or the songs of a popular rock group, and they might find these equally meaningless.

Like language, another arrangement of sounds, music is a uniquely human form of communication with well-developed rules of construction much like grammar. Some language experts would say that you can listen to someone speaking a language you do not understand and still know whether the speaker is excited or tired, angry or delighted. You would be making interpretations based upon the speech patterns: loud or soft, high-pitched or low-pitched, rapid and bitten off, or slow and smooth. Corresponding to these elements of speech are musical variables such as dynamics (force and volume), register (range of music or voice), mode (arrangement of a set of tones), and articulation (such as staccato, meaning abrupt and crisp; or legato, smooth and even). On the other hand, most people would agree that a meaningful conversation can only take place when both the speaker and the listener speak the same language. The conversation becomes even more meaningful when the parties are talking about something or someone they both know well.

Although there is no general agreement as to exactly what music communicates or how it communicates it, some individuals and governments have believed that music possesses great powers of communication. Most ancient Greek philosophers believed that listening to music based on certain of the modes in use at the time was beneficial to the development of a young person’s character, and warned that listening to music based on certain other modes would have harmful effects. For centuries Chinese beliefs about music were influenced by the philosophy of Confucius, whichmusic was not to entertain but to purify one's thoughts.